using System.Text.RegularExpressions;

namespace Tequila.Phone.Sharing
{
    internal static class Extensions
    {
        internal static string TransformHtmlToPlain(this string source)
        {
            try
            {
                // Remove HTML Development formatting
                // Replace line breaks with space
                // because browsers inserts space
                var result = source.Replace("\r", " ");
                // Replace line breaks with space
                // because browsers inserts space
                result = result.Replace("\n", " ");
                // Remove step-formatting
                result = result.Replace("\t", string.Empty);
                // Remove repeating spaces because browsers ignore them
                result = Regex.Replace(result,
                                                                      @"( )+", " ");

                // Remove the header (prepare first by clearing attributes)
                result = Regex.Replace(result,
                         @"<( )*head([^>])*>", "<head>",
                         RegexOptions.IgnoreCase);
                result = Regex.Replace(result,
                         @"(<( )*(/)( )*head( )*>)", "</head>",
                         RegexOptions.IgnoreCase);
                result = Regex.Replace(result,
                         "(<head>).*(</head>)", string.Empty,
                         RegexOptions.IgnoreCase);

                // remove all scripts (prepare first by clearing attributes)
                result = Regex.Replace(result,
                         @"<( )*script([^>])*>", "<script>",
                         RegexOptions.IgnoreCase);
                result = Regex.Replace(result,
                         @"(<( )*(/)( )*script( )*>)", "</script>",
                         RegexOptions.IgnoreCase);
                //result = Regex.Replace(result,
                //         @"(<script>)([^(<script>\.</script>)])*(</script>)",
                //         string.Empty,
                //         RegexOptions.IgnoreCase);
                result = Regex.Replace(result,
                         @"(<script>).*(</script>)", string.Empty,
                         RegexOptions.IgnoreCase);

                // remove all styles (prepare first by clearing attributes)
                result = Regex.Replace(result,
                         @"<( )*style([^>])*>", "<style>",
                         RegexOptions.IgnoreCase);
                result = Regex.Replace(result,
                         @"(<( )*(/)( )*style( )*>)", "</style>",
                         RegexOptions.IgnoreCase);
                result = Regex.Replace(result,
                         "(<style>).*(</style>)", string.Empty,
                         RegexOptions.IgnoreCase);

                // insert tabs in spaces of <td> tags
                result = Regex.Replace(result,
                         @"<( )*td([^>])*>", "\t",
                         RegexOptions.IgnoreCase);

                // insert line breaks in places of <BR> and <LI> tags
                result = Regex.Replace(result,
                         @"<( )*br([ /])*>", "\r",
                         RegexOptions.IgnoreCase);
                result = Regex.Replace(result,
                         @"<( )*li( )*>", "\r",
                         RegexOptions.IgnoreCase);

                // insert line paragraphs (double line breaks) in place
                // if <P>, <DIV> and <TR> tags
                result = Regex.Replace(result,
                         @"<( )*div([^>])*>", "\r\r",
                         RegexOptions.IgnoreCase);
                result = Regex.Replace(result,
                         @"<( )*tr([^>])*>", "\r\r",
                         RegexOptions.IgnoreCase);
                result = Regex.Replace(result,
                         @"<( )*p([^>])*>", "\r\r",
                         RegexOptions.IgnoreCase);

                // Remove remaining tags like <a>, links, images,
                // comments etc - anything that's enclosed inside < >
                result = Regex.Replace(result,
                         @"<[^>]*>", string.Empty,
                         RegexOptions.IgnoreCase);

                // replace special characters:
                result = Regex.Replace(result,
                         @" ", " ",
                         RegexOptions.IgnoreCase);

                result = Regex.Replace(result,
                         @"&bull;", " * ",
                         RegexOptions.IgnoreCase);
                result = Regex.Replace(result,
                         @"&lsaquo;", "<",
                         RegexOptions.IgnoreCase);
                result = Regex.Replace(result,
                         @"&rsaquo;", ">",
                         RegexOptions.IgnoreCase);
                result = Regex.Replace(result,
                         @"&trade;", "(tm)",
                         RegexOptions.IgnoreCase);
                result = Regex.Replace(result,
                         @"&frasl;", "/",
                         RegexOptions.IgnoreCase);
                result = Regex.Replace(result,
                         @"&lt;", "<",
                         RegexOptions.IgnoreCase);
                result = Regex.Replace(result,
                         @"&gt;", ">",
                         RegexOptions.IgnoreCase);
                result = Regex.Replace(result,
                         @"&copy;", "(c)",
                         RegexOptions.IgnoreCase);
                result = Regex.Replace(result,
                         @"&reg;", "(r)",
                         RegexOptions.IgnoreCase);
                result = Regex.Replace(result,
                         @"&nbsp;", " ",
                         RegexOptions.IgnoreCase);
                // Remove all others. More can be added, see
                // http://hotwired.lycos.com/webmonkey/reference/special_characters/
                result = Regex.Replace(result,
                         @"&(.{2,6});", string.Empty,
                         RegexOptions.IgnoreCase);

                // for testing
                //Regex.Replace(result,
                //       this.txtRegex.Text,string.Empty,
                //       RegexOptions.IgnoreCase);

                // make line breaking consistent
                result = result.Replace("\n", "\r");

                // Remove extra line breaks and tabs:
                // replace over 2 breaks with 2 and over 4 tabs with 4.
                // Prepare first to remove any whitespaces in between
                // the escaped characters and remove redundant tabs in between line breaks
                result = Regex.Replace(result,
                         "(\r)( )+(\r)", "\r\r",
                         RegexOptions.IgnoreCase);
                result = Regex.Replace(result,
                         "(\t)( )+(\t)", "\t\t",
                         RegexOptions.IgnoreCase);
                result = Regex.Replace(result,
                         "(\t)( )+(\r)", "\t\r",
                         RegexOptions.IgnoreCase);
                result = Regex.Replace(result,
                         "(\r)( )+(\t)", "\r\t",
                         RegexOptions.IgnoreCase);
                // Remove redundant tabs
                result = Regex.Replace(result,
                         "(\r)(\t)+(\r)", "\r\r",
                         RegexOptions.IgnoreCase);
                // Remove multiple tabs following a line break with just one tab
                result = Regex.Replace(result,
                         "(\r)(\t)+", "\r\t",
                         RegexOptions.IgnoreCase);
                // Initial replacement target string for line breaks
                var breaks = "\r\r\r";
                // Initial replacement target string for tabs
                var tabs = "\t\t\t\t\t";
                for (var index = 0; index < result.Length; index++)
                {
                    result = result.Replace(breaks, "\r\r");
                    result = result.Replace(tabs, "\t\t\t\t");
                    breaks = breaks + "\r";
                    tabs = tabs + "\t";
                }

                // custom
                result = result.TrimStart(" ".ToCharArray());
                result = Regex.Replace(result, "^\r\r", "\r");
                result = Regex.Replace(result, "\r\r\r", "\r\r");

                result = result.Replace("\r", "\n");

                // That's it.
                return result;

            }
            catch
            {
                return source;
            }
        }

    }
}